1. Field of the Invention
The present invention relates to a technology for controlling communication between a main body of an image forming apparatus (an image forming apparatus main body) for forming an image by an electrophotographic process such as a copier or a printer and an optional apparatus attached to the image forming apparatus main body.
2. Description of the Related Art
Up to now, multiple optional apparatuses attachable to an image forming apparatus main body are connected to an image forming apparatus. While communicating with the optional apparatuses (slaves), the image forming apparatus main body (master) controls the optional apparatuses to execute a cooperative operation of conveyance for sheet feeding and sheet discharging, or the like.
For example, Japanese Patent Application Laid-Open No. 2006-133996 and Japanese Patent Application Laid-Open No. 2006-225108 disclose the image forming apparatus main body that performs communication with multiple cascade-connected optional apparatuses. One identification number (also called “ID number”) is assigned to one optional apparatus connected to the image forming apparatus main body. Meanwhile, the optional apparatus permits a communication connection to another optional apparatus cascade-connected thereto.
By repeating assigning another identification number to another optional apparatus to which a communication connection is newly established, the image forming apparatus main body assigns separate identification numbers to all the optional apparatuses. In order to communicate with one specific optional apparatus, the image forming apparatus main body transmits communication data including an identification number thereof. Of the optional apparatuses that have received the identification number, only one optional apparatus having the corresponding identification number processes communication.
There is increasing demand that the optional apparatuses as described above have such flexibility after their release that a new optional apparatus desired by a user can be developed and connected to the image forming apparatus main body. In addition, less expensive optional apparatuses have been desired.
For example, it is assumed that optional sheet feeding apparatuses are connected to the image forming apparatus main body in such a manner that, at the time of their release, up to four optional sheet feeding apparatuses each having one sheet feeding function (one sheet feeding cassette) are stacked one upon another. It is possible that, after the above-mentioned release, optional sheet feeding apparatuses are added in such a manner that up to two optional sheet feeding apparatuses each having two sheet feeding functions (such an integral type as to have two cassettes with the reduced number of component parts and with the reduced costs because of sharing one control portion (unit) including a CPU on a slave side) are stacked one upon another (to have up to four sheet feeding functions in total).
The above-mentioned case of adding such a new optional sheet feeding apparatus as to have multiple sheet feeding mechanisms and one control device including a CPU as a slave leads to the following problem. That is, in the case where one optional apparatus has multiple sheet feeding functions, if the ID number is assigned to each optional apparatus, each sheet feeding function cannot be separately designated only by the ID number. As a result, there is a problem that each sheet feeding function cannot be controlled in a satisfactory manner.
Meanwhile, an upgrade has been carried out for adding communication specifications and conveyance control specifications corresponding to the new optional apparatus to the control portion of the image forming apparatus main body. As a result, if the upgrade is not carried out for the control device of the image forming apparatus main body, there occurs a problem that a newly purchased optional apparatus will not work after being attached thereto. In addition, at the time of product development before the release, all kinds of optional apparatus configuration that are to be requested by the users in the future cannot be expected, and hence the image forming apparatus main body cannot be caused to prestore information on all kinds of optional apparatus configuration, communication specifications thereof, or conveyance control specifications thereof.